Then run ‘ifconfig <eth> down’ on the server, or unplug the network cable. Watch the session on the switch and you will see which port has its link status change.

This isn’t a replacement for proper labels, since it involves downing an active network interface, which could cause connectivity issues in a live environment. A better alternative would be to use LLDP to identify which port a server is connected to, but as the title says, this is the lazy way.